Sterndrive Engineering Mercury Outboard 3.0L Replacement Lower Unit 1.75:1, 20" DriveshaftNote for purchasing: You must verify your Gear Ratio. Call for application assistance if needed, and have your engine serial number ready when calling. SE216, 1.75:1, 20" Driveshaft; Replaces Most Mercury 3.0L Lower Units - 13 Splines For SEI 216-218; Includes Sterndrive Engineering's No Fault Warranty for 3 Years; The SEI 216 gear cases are supplied with the correct water tube coupling for units with a serial number of OG438000 and higher. If your unit has a lower serial number, you will need to use your old water coupling or purchase the correct part. 20" 45-824114A 1; 25" 45-823901A 1; 30" 45-824115A 1 (This shaft is no longer available from the OE. You will need to either source a used one or repair your old unit.); Click to Download Sterndrive Engineering SE216 Lower Unit Installation Instructions Item is subject to a 20% restocking fee (Boat Covers, Bimini Tops, Outdrives, Drop Ship Items and Special Order Parts)!**Year, Serial Number, and Horsepower are required to order. Please contact us with this information after you place your order otherwise processing will be delayed.